The proposed program of research is dedicated to the development of sophisticated animal models for the study of speech and communication disorders. Speech and vocal communication are biopsychological phenomena: a full understanding of them is dependent upon approaching them as systems and understanding what they must be designed to accomplish, and what impediments they must overcome in nature. Under natural conditions vocal signals are embedded in background noises and are degraded by the action of diffraction, reflection and refraction. This research program, employing non-invasive behavioral methods, focuses on the detection, discrimination and classification of vocal signals by nonhuman primates and the impairment of these processes by ecological factors. One goal of this research is to identify specializations in phonation and reception that act to counter the impediments to communication found in nature. Complementing this ecological perspective the research program addresses the measurement of motor processes underlying vocal production. Vocal communication requires coordination of the twin processes of production and perception, and one objective of this research is to study the interrelationships between these processes. A final mission of this research is to develop a graded series of experiments involving the detection, discrimination and classification of vocal signals that are designed to distinguish between acoustic and phonetic or species-specific modes of perception. The identification of perceptual abilities specific to particular organisms or specific to particular vocal gestures is important for the study of the neural mechanisms underlying speech.